Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review A

Velocity distributions and diffusion tensor modified by broadband irradiation

Stanisław Kryszewski, Gerard Nienhuis

Published Oct 1, 1987• 10 citations
Publisher

Abstract

We evaluate the velocity distributions for both atomic states for optically active two-state atoms immersed in a buffer gas and irradiated with a broadband radiation field. Collisions with buffer-gas particles are assumed to be completely thermalizing and the collision rates are state dependent. Furthermore, we calculate the drift velocity and the anisotropic diffusion tensor as functions of various parameters of the system. In particular we give explicit results for the case of a spectral distribution in the shape of a step function. The results determine the basic equations for light-induced drift and diffusive pulling.

DOI
10.1103/physreva.36.3819

Related papers

General diffusion equation for light-induced drift

Gerard Nienhuis, Stanisław Kryszewski

We derive a general diffusion equation for the density of an atomic vapor immersed in a buffer gas and irradiated by nearly resonant light. The combination of velocity-selective excitation with state-dependent rates of velocity-changing collisions then gives rise to a drift term, and at the same time the diffusion tensor becomes anisotropic and intensity dependent. Both the effect of light-induced drift and diffusive pulling of atoms by the light are described by this diffusion equation in a consistent and correlated fashion.

Physical Review A•Aug 1, 1987•18 citations

Modelling gas-kinetic effects of light on gases with Keilson-Storer collision kernels

S Kryszewski, Gerard Nienhuis

The authors consider a system of optically active two-state atoms immersed in a buffer gas and irradiated by a light beam. The corresponding Bloch equations are augmented by Keilson-Storer (KS) collision kernels (1952) which account for velocity-changing collisions. Expansion of the density operator elements in the eigenfunctions of KS kernels allows one to obtain exact solutions for the Laplace transforms of the density operator elements which may be expressed as rational approximants with any prescribed degree of accuracy. As an example they apply this method to discussion of the light-induced drift effect. In particular they give analytic expressions for the drift velocity, which are illustrated by numerical results. Finally, they briefly discuss possible generalisations and applications of the presented method.

Journal of Physics B Atomic and Molecular Physics•Jul 14, 1987•17 citations

A new aspect of the velocity redistribution of atoms induced by a light beam and collisions: the atomic drift effect

S Zielinska

A simple method which allows one to study the influence of all relaxation processes and the pumping rate on the velocity distribution of the two-level atom populations is reviewed. In particular, the author presents a treatment that consistently includes the effects of phase and velocity relaxation on the atomic coherences. This method is applied to describe the drift of absorbing atoms-the effect which is also named light-induced gas diffusion. The results of numerical calculations for the drift velocity are presented and the role of the atomic coherences in the description of this phenomenon is pointed out. The dependence of the drift velocity on various parameters is discussed and the best experimental conditions for observing this effect are suggested.

Journal of Physics B Atomic and Molecular Physics•Apr 14, 1985•11 citations

White-light-induced drift in a gas with one optically active species

Alan D. Streater

A new light-induced drift effect is discussed in which a white-light source separates a gas mixture containing a single optically active (absorbing) species and a buffer gas which does not interact with the light. A three-level model with one upper level and two closely spaced lower levels is used for the active atoms, and strong collisions with the more abundant surrounding buffer gas atoms are assumed. The intensity spectrum in the vapor (including the effects of hyperfine pumping), and the resulting drift velocity are calculated as a function of optical depth into the vapor.

Physical Review A•Jan 1, 1990•8 citations

Modelling light-induced kinetic effects in gases with eigenvalues of collision operators

S Kryszewski, Gerard Nienhuis

The authors consider a system of two-level atoms coupled to a radiation field and immersed in a buffer gas. The corresponding Bloch-like equations are augmented by collision operators stemming from the linear Boltzmann equation. Collision operators describe velocity-changing collisions that give rise to various kinetic effects of light. They study the general properties of collision operators, the main one consisting of the fact that such operators are Hermitian in a suitably defined space of velocity distribution functions They introduce a set of functions that serve as approximations to the eigenfunctions. The eigenvalues are connected with transport coefficients (they give an example of such a relation), but they keep eigenvalues as free parameters of the approach. In this way the authors can describe the whole class of collision operators, the Keilson-Storer model being a particular example. Employing the introduced eigenfunctions they derive and formally solve the equations of motion for the expansion coefficients of the elements of the density matrix of active atoms.

Journal of Physics B Atomic Molecular and Optical Physics•Nov 14, 1989•10 citations

On the accuracy of a one-dimensional approach to the solution of kinetic equations with velocity-dependent collision frequencies

А. И. Пархоменко, Anatolii M. Shalagin

The solution of many problems in light-induced gas kinetics can be simplified significantly using quantum kinetic equations in the context of the so-called one-dimensional approximation, in which the initial equations are averaged over transverse (relative to the direction of radiation) velocities. The errors introduced in such an approach are usually assumed to be small; however, this has been confirmed quantitatively only on the basis of the simplest (two- and three-level) particle models. We analyze the accuracy of the one-dimensional approximation for multilevel particles quantitatively for the light-induced drift (LID) effect in cesium atoms in the atmosphere of inert buffer gases. It is shown that in the case of the so-called “normal” LID, one-dimensional kinetic equations can always be used instead of three-dimensional equations without a risk of losing some important fine details in the dependence of the drift velocity on the radiation frequency. In the case of anomalous LID, the error of the one-dimensional approximation is also insignificant, but it can be disregarded only in the case of light buffer particles. For comparable masses of resonant and buffer particles, the one-dimensional approximation may give a noticeable error in determination of drift velocity amplitudes; however, the positions of drift velocity zeros and extrema depending on radiation-frequency detuning can be described successfully. Results show that the error introduced by using the one-dimensional approximation for multilevel particles turns out to be more significant than for the simplest particle models.

Journal of Experimental and Theoretical Physics•Nov 1, 2014•2 citations
We evaluate the velocity distributions for both atomic states for optically active two-state atoms immersed in a buffer gas and irradiated with a broadband radiation field. Collisions with buffer-gas particles are assumed to be completely thermalizing and the collision rates are state dependent. Furthermore, we calculate the drift velocity and the anisotropic diffusion tensor as functions of various parameters of the system. In particular we give explicit results for the case of a spectral distribution in the shape of a step function. The results determine the basic equations for light-induced drift and diffusive pulling.
We derive a general diffusion equation for the density of an atomic vapor immersed in a buffer gas and irradiated by nearly resonant light. The combination of velocity-selective excitation with state-dependent rates of velocity-changing collisions then gives rise to a drift term, and at the same time the diffusion tensor becomes anisotropic and intensity dependent. Both the effect of light-induced drift and diffusive pulling of atoms by the light are described by this diffusion equation in a consistent and correlated fashion.
The authors consider a system of optically active two-state atoms immersed in a buffer gas and irradiated by a light beam. The corresponding Bloch equations are augmented by Keilson-Storer (KS) collision kernels (1952) which account for velocity-changing collisions. Expansion of the density operator elements in the eigenfunctions of KS kernels allows one to obtain exact solutions for the Laplace transforms of the density operator elements which may be expressed as rational approximants with any prescribed degree of accuracy. As an example they apply this method to discussion of the light-induced drift effect. In particular they give analytic expressions for the drift velocity, which are illustrated by numerical results. Finally, they briefly discuss possible generalisations and applications of the presented method.
A simple method which allows one to study the influence of all relaxation processes and the pumping rate on the velocity distribution of the two-level atom populations is reviewed. In particular, the author presents a treatment that consistently includes the effects of phase and velocity relaxation on the atomic coherences. This method is applied to describe the drift of absorbing atoms-the effect which is also named light-induced gas diffusion. The results of numerical calculations for the drift velocity are presented and the role of the atomic coherences in the description of this phenomenon is pointed out. The dependence of the drift velocity on various parameters is discussed and the best experimental conditions for observing this effect are suggested.
A new light-induced drift effect is discussed in which a white-light source separates a gas mixture containing a single optically active (absorbing) species and a buffer gas which does not interact with the light. A three-level model with one upper level and two closely spaced lower levels is used for the active atoms, and strong collisions with the more abundant surrounding buffer gas atoms are assumed. The intensity spectrum in the vapor (including the effects of hyperfine pumping), and the resulting drift velocity are calculated as a function of optical depth into the vapor.
The authors consider a system of two-level atoms coupled to a radiation field and immersed in a buffer gas. The corresponding Bloch-like equations are augmented by collision operators stemming from the linear Boltzmann equation. Collision operators describe velocity-changing collisions that give rise to various kinetic effects of light. They study the general properties of collision operators, the main one consisting of the fact that such operators are Hermitian in a suitably defined space of velocity distribution functions They introduce a set of functions that serve as approximations to the eigenfunctions. The eigenvalues are connected with transport coefficients (they give an example of such a relation), but they keep eigenvalues as free parameters of the approach. In this way the authors can describe the whole class of collision operators, the Keilson-Storer model being a particular example. Employing the introduced eigenfunctions they derive and formally solve the equations of motion for the expansion coefficients of the elements of the density matrix of active atoms.
The solution of many problems in light-induced gas kinetics can be simplified significantly using quantum kinetic equations in the context of the so-called one-dimensional approximation, in which the initial equations are averaged over transverse (relative to the direction of radiation) velocities. The errors introduced in such an approach are usually assumed to be small; however, this has been confirmed quantitatively only on the basis of the simplest (two- and three-level) particle models. We analyze the accuracy of the one-dimensional approximation for multilevel particles quantitatively for the light-induced drift (LID) effect in cesium atoms in the atmosphere of inert buffer gases. It is shown that in the case of the so-called “normal” LID, one-dimensional kinetic equations can always be used instead of three-dimensional equations without a risk of losing some important fine details in the dependence of the drift velocity on the radiation frequency. In the case of anomalous LID, the error of the one-dimensional approximation is also insignificant, but it can be disregarded only in the case of light buffer particles. For comparable masses of resonant and buffer particles, the one-dimensional approximation may give a noticeable error in determination of drift velocity amplitudes; however, the positions of drift velocity zeros and extrema depending on radiation-frequency detuning can be described successfully. Results show that the error introduced by using the one-dimensional approximation for multilevel particles turns out to be more significant than for the simplest particle models.